Throttle valve device

ABSTRACT

A throttle valve device ideal for small, inexpensive implements is provided. The throttle valve device having a damping member for slowly closing a throttle valve. The throttle valve device ( 1 ) has a throttle valve ( 4 ) that is fixed to a throttle shaft ( 5 ) pivotably supported in an air intake passage ( 2 ) and that is urged towards the closed direction, the throttle valve ( 4 ) adapted for adjusting the amount of air passing through the air intake passage ( 2 ). A through-bore ( 31 ) penetrating a shaft bore of the throttle shaft ( 5 ) is formed in a body, and a damping member ( 8 ) having frictional capabilities is inserted into and supported in the through-bore ( 31 ) in a state of pressing against the throttle shaft ( 5 ) inserted through the shaft bore ( 51 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a throttle valve device in which athrottle valve for adjusting the amount of air passing through an airintake passage is fixed to a throttle shaft pivotably supported in theair intake passage.

2. Description of the Related Art

Conventionally, throttle valve devices are known in which a throttlevalve for adjusting the amount of air passing through an air intakepassage is fixed to a throttle shaft pivotably supported in the airintake passage. These devices are used, for example, as a means forcontrolling the amount of air intake to an engine with comparative ease.

Also, emissions reduction strategies have improved fuel efficiencyduring idling in, for example, throttle valve devices used in engines,with the throttle valve being urged towards the closed direction so thatthe valve swiftly returns to the idle position when the acceleratorlever is disengaged.

Therefore, a problem has been presented in that the throttle valvequickly returns to idle position when the engine is returned fromhigh-speed rotation to idle rotation, leading to a decreased air-fuelratio (“rich” state) and causing engine stalling, increased emissions,and the like.

Thus, conventionally it is typical to additionally provide a dampingmember such as a cylinder (dashpot) using air or a fluid, as describedin Unexamined Japanese Patent Application Publication 59-65633, assimple means for causing the throttle valve to close slowly, increasingthe amount of time taken to close. This is to prevent a rich air-fuelratio and a precipitous drop in engine rotation speed when the throttlelever in the engine of an automobile or the like is returned fromhigh-speed rotation.

However, a problem has been presented in that, while it has beenpossible to provide a damping member such as the dashpot described abovein products having an engine compartment with a comparatively highvolume or in expensive products, as is the case with automobiles, in thecase of engines used in small, handheld implements such as, for example,chainsaws or trimmers, the addition of a damping member such as adashpot not only increases weight but is not feasible in terms of eitherspace or price.

SUMMARY OF THE INVENTION

The present invention, which was conceived in an attempt to resolve theabove problems, provides a throttle valve ideal for use in small devicesand comparatively inexpensive implements.

The throttle valve device of the present invention, which was conceivedto resolve the problems described above, has a throttle valve that isfixed to a throttle shaft pivotably supported in an air intake passageand that is urged towards the closed direction, the throttle valveadapted for adjusting the amount of air passing through the air intakepassage; the throttle valve device characterized in that a through-borepenetrating a shaft bore of the throttle shaft is formed in a bodyhaving the air intake passage formed therein, and a damping memberhaving frictional capabilities is inserted into and supported in thethrough-bore in a state of pressing against the throttle shaft insertedthrough the shaft bore.

According to the present invention, the damping member having frictionalcapabilities presses against an outer circumference of the throttleshaft, thereby appropriately braking the rotation of the throttle shaftand increasing the amount of time taken for the throttle valve to returnto idle position from high speed. The occurrence of a rich state isthereby prevented when the throttle valve returns to idle position.

In a case where the damping member is formed using an elastic materialand is inserted and supported in a state of being pressed against thethrottle shaft by a clamp bolt threaded into the through-bore, theinvention can be readily and inexpensively implemented employing aconstruction involving few parts. In a case where a compression springmember is disposed between the damping member and the clamp bolt, amaterial other than an elastic material can be used as the dampingmember.

Furthermore, in the present invention, in a case where the dampingmember is a spherical body, contact will be made with the throttle shaftover a small area; and, particularly in a case where the damping memberis formed using an elastic material, the damping member will readilydemonstrate its elasticity on being suitably compressed.

Furthermore, if the damping member is columnar in shape and a distal endsurface thereof constituting a surface that contacts the throttle shaftforms a concave portion following along the outer circumference of thethrottle shaft, the contact area will always remain the same. Therefore,the damping member can be used stably over a long period of time.

According to the present invention, it is possible to provide a throttlevalve device ideal for use with small, inexpensive implements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a preferred embodiment of the presentinvention;

FIG. 2 is an enlarged perspective view of a damping member in theembodiment represented in FIG. 1;

FIG. 3 is an enlarged perspective view of another embodiment of thedamping member of the present invention; and

FIG. 4 is an enlarged perspective view of yet another embodiment of thedamping member of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The present invention will be described below based on embodiments shownin the drawings.

FIGS. 1 and 2 illustrate a preferred embodiment of the throttle valvedevice of the present invention in a carburetor application. In athrottle valve device 1, a throttle valve 4 for adjusting the amount ofair flowing through an air intake passage 2 into a throttle body 3 inwhose interior the air intake passage 2 is formed is fixed to a throttleshaft 5 pivotably supported in the air intake passage 2 of the throttlebody 3.

An urging device 6 formed using a coil spring is additionally providedon the throttle shaft 5, and is set so that the throttle valve 4 fixedto the throttle shaft 5 is constantly urged towards the closed directionand constantly returns to idle position when a throttle lever 7 fixed toan end of the throttle shaft 5 is released.

A through-bore 31 penetrating a shaft bore 51 of the throttle shaft 5 isformed in the throttle body 3, and a spherical damping member 8 havingfrictional capabilities and being made of, for example, a stable rubbermaterial is inserted into the through-bore 31. A clamp bolt 81 isthreaded into the through-bore 31 from the outside, and the dampingmember 8 is supported in a state of being pressed against the throttleshaft 5.

As in conventional throttle valve devices, according to the presentembodiment configured as described above, a throttle lever 7 affixed toan end of the throttle shaft 5 is caused to rotate against the urgingforce of the urging device 6 via, for example, a connected acceleratorwire, thereby causing the throttle shaft 5 to rotate in the opendirection, opening the throttle valve 4 provided in the air intakepassage 2, and increasing the amount of air drawn in, whereby the engineis made to rotate at higher speed.

When, in order to cease high-speed rotation, an accelerator (notillustrated) is released and the throttle lever 7 is returned to theoriginal idle position, the throttle shaft 5 fixed to the throttle lever7 rotates towards the closed direction due to the urging force of theurging device 6, returning to the original idle position. In thisembodiment, a damping member 8 having frictional force is in contactwith the throttle shaft 5 in a state of being pressed against the shaft,so that the return to the idle position occurs slowly over time ratherthan suddenly, as in conventional examples.

Therefore, it is possible to effectively prevent precipitous drops inengine rotation speed, stalling of the engine, and emission of exhaustgases or the like as caused by the air-fuel ratio being rich when thethrottle shaft 5 returns to the idle position.

In particular, in the present embodiment, it is acceptable merely for athrough-bore 31 communicating with the shaft bore 51 of the throttleshaft 5 to be formed in the throttle body 3 and for the damping member 8to be supported in a pressed state therein. The present embodiment doesnot differ in external appearance from the prior art; it is readilyconstructed, light in weight, and capable of being inexpensivelyprovided. The present embodiment is ideally used in engines installed insmall, comparatively inexpensive hand-held devices such as chainsaws andtrimmers.

In particular, since only the damping member 8 and the clamp bolt 81 arenecessary in the present embodiment, the number of parts can be keptsmall. Also, by virtue of the damping member 8 comprising an elasticmaterial, it can be readily supported in a state of pressing against thethrottle shaft merely by the clamp bolt 81 being pressed against thedamping member.

FIGS. 3 and 4 illustrate another embodiment of the damping member 8according to the present invention. FIG. 3 depicts a compression springmember 82 disposed between the damping member 8 and the clamp bolt 81.An advantage is presented in the present embodiment in that a materialother than an elastic material can be used for the damping member 8,which is preferable in instances where high friction or durability isrequired.

In the embodiment illustrated in FIG. 4, the damping member 8 iscolumnar in shape, a concave portion fitting the outer circumference ofthe throttle shaft 5 is formed in a surface 83 contacting the throttleshaft 5, the surface 83 being a distal end surface of the damping member8, and a greater contact surface can be obtained. This embodiment can beapplied when high friction is necessary.

While an instance of the present embodiment being used in a carburetorhas been described, it shall be apparent that the present invention canalso be applied to other implements in which an air intake passage iscontrolled.

KEY

-   -   1 Throttle valve device    -   2 Air intake passage    -   3 Throttle body    -   4 Throttle valve    -   5 Throttle shaft    -   6 Urging device    -   7 Throttle lever    -   8 Damping member    -   81 Clamp bolt

While the invention is susceptible to various modifications, andalternative forms, specific examples thereof have been shown in thedrawings and are herein described in detail. It should be understood,however, that the invention is not to be limited to the particular formsor methods disclosed, but to the contrary, the invention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the appended claims.

The invention claimed is:
 1. A throttle valve device in a carburetorcomprising a throttle valve that is fixed to a throttle shaft pivotablysupported in an air intake passage through a carburetor body and that isurged towards the closed direction, the throttle valve adapted foradjusting the amount of air passing through the air intake passage,wherein the throttle valve device comprises a shaft bore formed in thecarburetor having the air intake passage formed therein, the shaft borereceiving the throttle shaft, a through-bore formed in the carburetorbody and penetrating the shaft bore of the carburetor body, and adamping member having frictional capabilities to dampen the rotation ofthe throttle shaft, the damping member is inserted into and supported inthe through-bore in a state of pressing against the throttle shaftreceived in the shaft bore.
 2. The throttle valve device according toclaim 1, wherein the damping member is formed using an elastic material;and the damping member is inserted and supported in a state of beingpressed against the throttle shaft by a clamp bolt threaded into thethrough-bore.
 3. The throttle valve device according to claim 1, whereina compression spring member is disposed between the damping member and aclamp bolt.
 4. The throttle valve device according to claim 2, wherein acompression spring member is disposed between the damping member and theclamp bolt.
 5. The throttle valve device according to claim 1, whereinthe damping member is a spherical body.
 6. The throttle valve deviceaccording to claim 2, wherein the damping member is a spherical body. 7.The throttle valve device according to claim 3, wherein the dampingmember is a spherical body.
 8. The throttle valve device according toclaim 1, wherein the damping member is columnar in shape, and a surfacecontacting the throttle shaft forms a concave portion that follows alongthe outer circumference of the throttle shaft, the contacting surfacebeing a distal end surface of the damping member.
 9. The throttle valvedevice according to claim 2, wherein the damping member is columnar inshape, and a surface contacting the throttle shaft forms a concaveportion that follows along the outer circumference of the throttleshaft, the contacting surface being a distal end surface of the dampingmember.
 10. The throttle valve device according to claim 3, wherein thedamping member is columnar in shape, and a surface contacting thethrottle shaft forms a concave portion that follows along the outercircumference of the throttle shaft, the contacting surface being adistal end surface of the damping member.